To meet the demand for wireless data traffic having increased since deployment of 4G communication systems, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’.
The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like.
In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
With the popularization of smartphones, data traffic is increasing rapidly. The increasing number of smartphone users spurs the consumption of smartphone-based application services such as SNS and games, resulting in an unprecedented increase in data traffic. Particularly, beyond the person-to-person communication, if the machine intelligent communication (such as person-to-machine and machine-to-machine communications) is activated as a new market field, the traffic concentration to the base station will exceed existing limitations.
There is therefore a need for a technology to solve such problems, and direct communication between devices is coming into the spotlight as one such technology. This so called Device to Device (D2D) communication technology is promising for the licensed band communication systems such as cellular communication systems and unlicensed band communication systems such as WLAN systems.
In the case of being combined with mobile communication, the D2D communication is attractive in terms of increasing traffic accommodation capability and reducing overload. That is, since the D2D communication is implemented in such a way that the User Equipments (UEs) located in the same cell or adjacent cells establish a D2D link and exchange data through the D2D link without involvement of any evolved Node B (eNB), it is advantageous to reduce the number of communication links from 2 to 1.
Researches on the unlicensed band aim to distinguish among person-to-person, person-to-machine, and machine-to-machine communications for protecting against unnecessary waste of radio resources and to provide the communication service in a local traffic-suited manner. That is, the focus is on a method for a plurality of devices to broadcast and receive the information on contents efficiently.
Unlike in the legacy ad-hoc/sensor networks, the D2D devices achieve synchronization therebetween first and then perform discovery, paring, and scheduling operations. This makes it possible to improve data and control signal transmission/reception efficiency and to configure a protocol efficiently for a scheduling scheme. That is, the synchronization-based D2D communication technology makes it possible for the distributed devices to communicate control signals efficiently and thus to consider the distributed protocol which has been difficult to be applied for controlling a network without any master node.
However, the distributed scheduling has a drawback in that it is difficult to accomplish maximum capacity because a single master node has to make a resource allocation decision based on partial information of each area without integral channel information of the whole network.
Implementing D2D communication over a cellular network is capable of compensating for problems which are difficult to be overcome in the distributed scheduling. There is therefore a need of an enhanced channel measurement method and apparatus for an eNB to allocate resources efficiently for D2D communication.